The grey matter in the brains of the homicidal children was not as dense. Grey matter helps control impulse and reaction. The thicker it is the better.

It appeared the brains of the boys who had killed weren’t as developed as they should be, and Kiehl said they were at a very high risk of poor, impulsive homicidal behavior.

“We asked a computer algorithm to classify homicide versus non-homicide and it got 85 percent correct, which is really amazing,” Kiehl said. “Our goal now is to help develop treatment that improves the structure, improves the density."

Kiehl began working with the state of Wisconsin, which has a rehabilitation program for troubled boys, some of whom have killed. They treat them with positive reinforcement techniques so they can learn control.

"So after a year of treatment, the boys who complete have a 50 percent less likely chance they're going to re-offend violently -- in a four year follow-up -- than the boys who don't get that treatment,” Kiehl said.

Kiehl is mapping the brains of the boys that go through the program to see, as they get treatment, if they’re literally changing, building up brain muscle density that will help them make better choices.

"We do believe that's the case,” Kiehl said. “We have preliminary evidence of 25 boys scanned before and after treatment and we do see change in the function of the brain -- and structure of the brain -- in regions of the brain that are known for re-offending."

Mind institute scientists are getting a bigger sample of those boys right now.

This type of program was just adopted by the state of Georgia, and Kiehl hopes one day New Mexico will also try it. He believes this is one of the most promising insights into understanding why some children kill and, better yet, how to help them.

“We are going to keep after it to reduce the chances of (school shootings) ever happening,” Kiehl said.

Ultimately Kiehl wants to find a way for troubled kids to be identified so their brains could be scanned. If they show low grey matter density, he said there would be a need for positive reinforcement before anything horrible happened.